2001 Toyota Echo noise/bump when braking

I have a 2001 Toyota Echo. Sometimes when I put the car in reverse and apply the brakes I hear a “clunk” and feel a “bump”. The brakes work fine; they’re not affected when this happens. (There’s no squeaking.) Occassionally this also happens when going forward, but both the clunk and bump are more frequent and stronger when going in reverse. (I’ve had the brakes checked out and have been told they’re fine.)

Thank you!